The WHO warns Zika is likely to spread throughout Asia after being detected in 70 countries.

Vietnam health ministry has said the number of confirmed Zika cases in the country has more than doubled over the past three days to 23, as a dozen new infections were recorded in Ho Chi Minh City, the commercial hub.

Last month, Vietnam raised the threat level for Zika and also increased the monitoring of pregnant women to keep a check on microcephaly cases. On Sunday, the Preventive Health Department confirmed the first case of microcephaly in Vietnam. The case was of a four-month-old child in the Central Highlands province of Dak Lak. The baby's mother was diagnosed with Zika.

Microcephaly is a state of severe birth defect in which the baby's head and brain are smaller than expected. Other brain abnormalities are quite common in such cases. It is caused by Zika virus, which was first identified in Uganda in 1947. More than 1,900 cases of microcephaly were confirmed in Brazil which is hardest hit so far.

In case of adults, Zika infections have also been linked to a rare neurological syndrome known as Guillain-Barre, as well as other neurological disorders.

There is no treatment or vaccine for Zika infection yet. Companies and scientists are working to develop a safe and effective vaccine for the virus. Zika is commonly said to be a close cousin of dengue and chikungunya.

According to the World Health Organisation (WHO), people infected with Zika can have symptoms including mild fever, skin rash, conjunctivitis, muscle and joint pain, malaise or headache. These symptoms of Zika normally last for two to seven days.

But reports show that an estimated 80 percent of Zika infected people do not have any symptoms. This makes it more difficult for people to understand whether they have been infected, especially for pregnant women.

Spreading throughout Asia

Last month, WHO said Zika was likely to spread throughout Asia after being detected in 70 countries, including at least 19 in the Asia-Pacific region.

Myanmar confirmed the first case of a Zika virus infected pregnant woman last Friday. The nationality of the woman was not disclosed by the authorities. She had been living in Myanmar for several years.

Among the Southeast Asian countries, Singapore and Thailand are the most Zika-affected countries with a total of about 800 cases, including dozens of pregnant women.